An Adaptive Linear Estimator Based Approach To Bi-Directional Motion Compensated Prediction

Bi-directional motion compensated prediction is widely utilized in video coding. Conventionally, the encoder searches for two motion vectors pointing to reference frames in both directions, and transmits these motion vectors to the decoder. Recognizing that the two reference frames are already available to the decoder, prior work proposed decoder-side motion estimation to extract motion information or optical flow, at the cost of dramatic increase in decoder complexity. This paper proposes a novel bi-directional motion compensation mode that efficiently utilizes the motion information that is already available to the decoder, without recourse to extensive search. An estimation theory based approach is proposed and utilized to provide a high quality prediction, which adaptively combines contributions from multiple motion-compensated references. Experimental results show that the proposed method, while yielding a greatly reduced decoder side complexity, introduces a significant coding gain for a diverse set of video sequences.